1. Field of the Invention
The present invention relates generally to a filtration apparatus for separating solid particles from a liquid. More particularly, the invention relates to filtration apparatus for removing particulate contaminants from commercial laundry wastewater and to methods for accomplishing the same.
2. State of the Art
State and local governments across the country as well as the federal government have enacted new laws or expanded existing laws to reverse or limit the threat of environmental pollution. These environmental laws are typically directed toward commercial enterprises which create various wastes streams as a by-product of manufacturing products or providing services. The commercial laundry industry and particularly commercial Laundromats are specifically affected by environmental laws which limit the amount of suspended solids or particulate contaminants in commercial laundry wastewater which can be discharged into the environment. Particulate contaminants in commercial laundry wastewater generally consist of lint, hair, dirt and soap scum. To meet the requirements of current environmental laws, the amount of particulate contaminants in commercial laundry wastewater must be reduced to an acceptable level before it is discharged into the ground water and/or municipal sewage system.
Co-owned U.S. Pat. No. 5,350,526 discloses a filtration apparatus specifically intended for removing particulate contaminants from commercial laundry wastewater. It has at least one porous mesh-like filter bag coupled between an inlet manifold for receiving wastewater containing particulate contaminants and an outlet manifold for discharging the particulate contaminants separated from the wastewater. The filter bag is agitated by a paddle, so as to prevent the mesh-like material of the filter bag from being clogged. The apparatus is capable of trapping particles as small as 5 microns depending on the filter bag mesh. Those skilled in the art will appreciate that the finer the mesh the more slowly the water will be filtered. One of the challenges in designing a filter for commercial laundry wastewater is to be able to accommodate a flow rate of about 12,500 gallons per day.
Co-owned U.S. Pat. No. 5,575,913 discloses a filtration apparatus having a housing, a filter element, an inlet, a first discharge outlet and a second discharge outlet. The housing includes a bottom and an upwardly extending surrounding wall. The filter element is disposed in the housing and spans the surrounding wall with the filter element spaced above the bottom of the housing to define an upper chamber and a lower chamber, and the filter element being angled, preferably 45 degrees from the horizontal, so that one end of the filter element is lower relative to the other end. The inlet is in fluid communication with the upper chamber for receiving wastewater containing particulate contaminants. A first discharge outlet is in fluid communication with the lower chamber for discharging filtered wastewater. The second discharge outlet is in fluid communication with the upper chamber adjacent the lower end of the filter element for discharging filtered particulate contaminants. The apparatus is capable of trapping particles about 50 microns in diameter (or smaller, i.e. 5-10 microns).
The previously incorporated parent application discloses a filtration apparatus which includes a rectangular tank having an upper baffle and a lower baffle, layers of stone and carbon between the baffles, a water inlet above the upper baffle, and a water outlet below the lower baffle. The filtration apparatus is preferably used in conjunction with other apparatus including additional filters, holding tanks, a backwash pump and air blower, and a leaching pool system. The preferred implementation includes a laundry waste sump, a primary 50 micron static screen filter, an array of 100 micron filter socks, a 9,000 gallon holding tank, a pair of 100 gallon surge tanks, a pair of parallel secondary carbon filters according to the invention, a 5 micron polishing filter, a backwash pump, an air blower, a 6,000 gallon sludge holding tank, and a system of four leaching pools. According to the preferred methods, the carbon filters are operated for fourteen hours continuously and backwashed for ten minutes every day. Each carbon filter operates at a flow rate of approximately 9,000 gallons per day and is backwashed with 450 gallons of water.
The previously incorporated related application discloses a filtration apparatus which includes a filter element disposed at a 45 degree angle defining an upper chamber for solids and a lower chamber for liquid. A trough is disposed at the lower end of the filter element. The floor of the trough funnels toward a central drain and an overflow drain is located approximately 8 inches above the trough floor. The lower chamber is provided with a drain for recirculating water to a sprayer above the filter element and is also provided with an overflow drain approximately 8 inches above the floor.
It is an object of the invention to provide an improved filtration apparatus and method for separating and removing particulate contaminants from a relatively large continuous flow of laundry wastewater for discharge of the filtered wastewater into the environment, i.e., ground water and/or municipal sewage system.
It is another object of the invention to provide such a filtration apparatus having a filter element for separating particulate contaminants from laundry wastewater in which the separated particulate contaminants can be easily and quickly manually or automatically removed from the apparatus without injuring or removing the filter element.
It is still yet another object of the present invention to provide such a filtration apparatus that is easily and inexpensively manufactured, highly efficient in operation, and which requires little lifetime maintenance.
In accord with these objects which will be discussed in detail below, the filtration apparatus of the present invention includes the filtration apparatus disclosed in either of the previously incorporated applications, but it is preferably the filtration apparatus disclosed in the related co-owned application Ser. No. 09/837,766. According to the invention, the filtration apparatus is used in conjunction with other apparatus including additional filters, holding tanks, a backwash pump and air compressor, and a leaching pool system.
A presently preferred implementation of the filtration apparatus includes a laundry waste sump, a primary 50 micron static screen filter (preferably as disclosed in previously incorporated Ser. No. 09/837,766), a single 100 micron filter sock, a 9,000 gallon holding tank, a pair of 100 gallon surge tanks, at least one secondary media filter, a 5 micron polishing filter, a backwash pump, an air blower, a 6,000 gallon sludge holding tank, one clear well, and a system of leaching pools. Wastewater enters the sump by gravity flow and is pumped from the sump to the primary 50 micron static screen filter. Solids removed by the primary filter are discharged by gravity to the 100 micron filter sock where they are dewatered with the water therefrom being returned to the sump. The primary effluent from the primary filter is delivered by gravity to the 9,000 gallon holding (equalization tank). Water from the equalization tank is pumped to the first 100 gallon surge tank from which it flows by gravity to the secondary media filter(s). The effluent from the media filter(s) is delivered by gravity to the second 100 gallon surge tank from which it is pumped through the 5 micron polishing filter into the clear well and from there to the leaching pools. Water from the clear well pool is used to backwash the media filter(s) using the backwash pump and the air blower which aerates the backwash water. Optionally, a source of fresh water may be used for backwash or mixed with the clear water for backwash. During backwash, backwash water exiting the media filter(s) is directed to the sludge holding tank(s).
According to the presently preferred methods of the invention, the carbon filters are operated for 14 to 23 hours continuously and backwashed for ten minutes every day. Each carbon filter operates at a flow rate of approximately 9,000 gallons per day and is backwashed with 450 gallons of water.
Additional objects and advantages of the invention will become apparent to those skilled in the art upon reference to the detailed description taken in conjunction with the provided figure.